This invention relates in general to devices for securing data discs and other record discs in releasable fashion, and more particularly to an apparatus for releasably securing a disc for high speed rotation especially during manufacture and testing.
In the fabrication of data discs, such as rigid "hard" discs used as recording medium in computer disc drives, there are many process steps in which each disc must be secured in releasable fashion to a rotatable arbor. Such process steps may include application of substances to the disc surface, cleaning, polishing, burnishing, and testing. In each of such steps, it is essential that the disc be secured firmly, extending perpendicularly to the axis of the rotating arbor, with virtually no wobble. Generally speaking, the prior art provides various forms of disc chucks adapted for automated operation, so that the placement and removal of the disc on the chuck may be carried out with robotic assitance.
Due to the fact that data discs have extremely fine tolerances for planarity, surface finish, and coating integrity, the devices used to hold the disc during processing must not impart any curvature to the disc and can grip the disc only at surface areas are not used for data recording.
There are some problems common to prior art disc chucks. The chuck may not be adapted to grip a disc that is not perfectly placed thereon. For example, if the robot tool that places the disc on the chuck errs slightly and does not locate the disc firmly on the land surface of the chuck, the typical prior art chuck may fail to grasp the disc, and the disc will be destroyed when the chuck begins to spin. Likewise, if the disc is not aligned perfectly perpendicular to the chuck axis of rotation, the chuck may fail to grip the chuck or may achieve a partial grip, which can also result in destruction of the disc. Furthermore, some chucks exert unequal pressure on the disc and produce curvature of the disc, resulting in an unusable product.